Set boto minimum version

For supporting the S3 multipart upload in glance,
set boto minimum version to 2.12.0.

Implements: blueprint s3-multi-part-upload
Change-Id: Id57a3887256a665455fd83d3e8e752a28c5e7659
Add oslo-incubator to automatic update

Change-Id: If422761221a21cfc0da08bd905c8e88f08a8fcce
Merge "Set boto minimum version"
Merge "Add oslo-incubator to automatic update"